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          <h1><!---->events - 事件与监听</h1>
          <div class="page-info"><span class="date-info" aria-label="写作日期📅" data-balloon-pos="down"><svg
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                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#events-emitter"
                    class="router-link-active router-link-exact-active toc-link level2">events.emitter()</a></li>
                <!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page" href="https://pro.autojs.org/docs/zh/v8/events.html#事件-exit"
                    class="router-link-active router-link-exact-active toc-link level2">事件: &#39;exit`</a></li>
                <!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-defaultmaxlisteners"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.defaultMaxListeners</a>
                </li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-addlistener-eventname-listener"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.addListener(eventName,
                    listener)</a></li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-emit-eventname-args"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.emit(eventName[,
                    ...args])</a></li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-eventnames"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.eventNames()</a>
                </li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-getmaxlisteners"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.getMaxListeners()</a>
                </li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-listenercount-eventname"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.listenerCount(eventName)</a>
                </li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-listeners-eventname"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.listeners(eventName)</a>
                </li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-on-eventname-listener"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.on(eventName,
                    listener)</a></li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-once-eventname-listener"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.once(eventName,
                    listener)#</a></li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-prependlistener-eventname-listener"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.prependListener(eventName,
                    listener)</a></li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-prependoncelistener-eventname-listener"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.prependOnceListener(eventName,
                    listener)</a></li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-removealllisteners-eventname"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.removeAllListeners([eventName])</a>
                </li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-removelistener-eventname-listener"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.removeListener(eventName,
                    listener)</a></li><!----><!--]--><!--[-->
                <li class="toc-item"><a aria-current="page"
                    href="https://pro.autojs.org/docs/zh/v8/events.html#eventemitter-setmaxlisteners-n"
                    class="router-link-active router-link-exact-active toc-link level2">EventEmitter.setMaxListeners(n)</a>
                </li><!----><!--]-->
              </ul>
            </div>
          </aside>
        </div><!---->
        <div class="theme-hope-content">
          <h1 id="events-事件与监听" tabindex="-1"><a class="header-anchor" href="#events-事件与监听" aria-hidden="true">#</a>
            events - 事件与监听</h1>
          <blockquote>
            <p>Stability: 2 - Stable</p>
          </blockquote>
          <p>events本身是一个<a href="#events_eventemitter">EventEmitter</a>。</p>
          <p>需要注意的是，事件的处理是单线程的，并且仍然在原线程执行，如果脚本主体或者其他事件处理中有耗时操作、轮询等，则事件将无法得到及时处理（会进入事件队列等待脚本主体或其他事件处理完成才执行）。</p>
          <h2 id="events-emitter" tabindex="-1"><a class="header-anchor" href="#events-emitter" aria-hidden="true">#</a>
            events.emitter()</h2>
          <p>返回一个新的<a href="#events_eventemitter">EventEmitter</a>。这个EventEmitter没有内置任何事件。</p>
          <h2 id="事件-exit" tabindex="-1"><a class="header-anchor" href="#事件-exit" aria-hidden="true">#</a> 事件:
            &#39;exit`</h2>
          <p>当脚本正常或者异常退出时会触发该事件。事件处理中如果有异常抛出，则立即中止exit事件的处理（即使exit事件有多个处理函数）并在控制台和日志中打印该异常。</p>
          <p>一个脚本停止运行时，会关闭该脚本的所有悬浮窗，触发exit事件，之后再回收资源。如果exit事件的处理中有死循环，则后续资源无法得到及时回收。
            此时脚本会停留在任务列表，如果在任务列表中关闭，则会强制结束exit事件的处理并回收后续资源。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&quot;开始运行&quot;</span><span class="token punctuation">)</span>
events<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&quot;exit&quot;</span><span class="token punctuation">,</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&quot;结束运行&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&quot;即将结束运行&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
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            </div>
          </div>
          <h1 id="eventemitter" tabindex="-1"><a class="header-anchor" href="#eventemitter" aria-hidden="true">#</a>
            EventEmitter</h1>
          <blockquote>
            <p>Stability: 2 - Stable</p>
          </blockquote>
          <h2 id="eventemitter-defaultmaxlisteners" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-defaultmaxlisteners" aria-hidden="true">#</a> EventEmitter.defaultMaxListeners</h2>
          <p>每个事件默认可以注册最多 10 个监听器。 单个 EventEmitter 实例的限制可以使用 emitter.setMaxListeners(n) 方法改变。 所有 EventEmitter 实例的默认值可以使用
            EventEmitter.defaultMaxListeners 属性改变。</p>
          <p>设置 EventEmitter.defaultMaxListeners 要谨慎，因为会影响所有 EventEmitter 实例，包括之前创建的。 因而，调用 emitter.setMaxListeners(n)
            优先于 EventEmitter.defaultMaxListeners。</p>
          <p>注意，与Node.js不同，<strong>这是一个硬性限制</strong>。 EventEmitter 实例不允许添加更多的监听器，监听器超过最大数量时会抛出TooManyListenersException。
          </p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>emitter<span class="token punctuation">.</span><span class="token function">setMaxListeners</span><span class="token punctuation">(</span>emitter<span class="token punctuation">.</span><span class="token function">getMaxListeners</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
emitter<span class="token punctuation">.</span><span class="token function">once</span><span class="token punctuation">(</span><span class="token string">&#39;event&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  <span class="token comment">// 做些操作</span>
  emitter<span class="token punctuation">.</span><span class="token function">setMaxListeners</span><span class="token punctuation">(</span>Math<span class="token punctuation">.</span><span class="token function">max</span><span class="token punctuation">(</span>emitter<span class="token punctuation">.</span><span class="token function">getMaxListeners</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">-</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
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            </div>
          </div>
          <h2 id="eventemitter-addlistener-eventname-listener" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-addlistener-eventname-listener" aria-hidden="true">#</a>
            EventEmitter.addListener(eventName, listener)</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any}</li>
            <li><code><span class="token property">listener</span></code> {Function}</li>
          </ul>
          <p>emitter.on(eventName, listener) 的别名。</p>
          <h2 id="eventemitter-emit-eventname-args" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-emit-eventname-args" aria-hidden="true">#</a> EventEmitter.emit(eventName[, ...args])
          </h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any}</li>
            <li><code><span class="token property">args</span></code> {any}</li>
          </ul>
          <p>按监听器的注册顺序，同步地调用每个注册到名为 eventName 事件的监听器，并传入提供的参数。</p>
          <p>如果事件有监听器，则返回 true ，否则返回 false。</p>
          <h2 id="eventemitter-eventnames" tabindex="-1"><a class="header-anchor" href="#eventemitter-eventnames"
              aria-hidden="true">#</a> EventEmitter.eventNames()</h2>
          <p>返回一个列出触发器已注册监听器的事件的数组。 数组中的值为字符串或符号。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code><span class="token keyword">const</span> myEE <span class="token operator">=</span> events<span class="token punctuation">.</span><span class="token function">emitter</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;foo&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;bar&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">const</span> sym <span class="token operator">=</span> <span class="token function">Symbol</span><span class="token punctuation">(</span><span class="token string">&#39;symbol&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span>sym<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>myEE<span class="token punctuation">.</span><span class="token function">eventNames</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 打印: [ &#39;foo&#39;, &#39;bar&#39;, Symbol(symbol) ]</span>
</code></pre>
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            </div>
          </div>
          <h2 id="eventemitter-getmaxlisteners" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-getmaxlisteners" aria-hidden="true">#</a> EventEmitter.getMaxListeners()</h2>
          <p>返回 EventEmitter 当前的最大监听器限制值，该值可以通过 emitter.setMaxListeners(n) 设置或默认为 EventEmitter.defaultMaxListeners。</p>
          <h2 id="eventemitter-listenercount-eventname" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-listenercount-eventname" aria-hidden="true">#</a>
            EventEmitter.listenerCount(eventName)</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {string} 正在被监听的事件名</li>
          </ul>
          <p>返回正在监听名为 eventName 的事件的监听器的数量。</p>
          <h2 id="eventemitter-listeners-eventname" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-listeners-eventname" aria-hidden="true">#</a> EventEmitter.listeners(eventName)</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {string}</li>
          </ul>
          <p>返回名为 eventName 的事件的监听器数组的副本。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>server<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token parameter">stream</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;someone connected!&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>util<span class="token punctuation">.</span><span class="token function">inspect</span><span class="token punctuation">(</span>server<span class="token punctuation">.</span><span class="token function">listeners</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 打印: [ [Function] ]</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
              <div class="line-number"></div>
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              <div class="line-number"></div>
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            </div>
          </div>
          <h2 id="eventemitter-on-eventname-listener" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-on-eventname-listener" aria-hidden="true">#</a> EventEmitter.on(eventName, listener)
          </h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any} 事件名</li>
            <li><code><span class="token property">listener</span></code> {Function} 回调函数</li>
          </ul>
          <p>添加 listener 函数到名为 eventName 的事件的监听器数组的末尾。 不会检查 listener 是否已被添加。 多次调用并传入相同的 eventName 和 listener 会导致
            listener 被添加与调用多次。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>server<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token parameter">stream</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;有连接！&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
              <div class="line-number"></div>
              <div class="line-number"></div>
              <div class="line-number"></div>
            </div>
          </div>
          <p>返回一个 EventEmitter 引用，可以链式调用。</p>
          <p>默认情况下，事件监听器会按照添加的顺序依次调用。 emitter.prependListener() 方法可用于将事件监听器添加到监听器数组的开头。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code><span class="token keyword">const</span> myEE <span class="token operator">=</span> events<span class="token punctuation">.</span><span class="token function">emitter</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;foo&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;a&#39;</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">prependListener</span><span class="token punctuation">(</span><span class="token string">&#39;foo&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;b&#39;</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">emit</span><span class="token punctuation">(</span><span class="token string">&#39;foo&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 打印:</span>
<span class="token comment">//   b</span>
<span class="token comment">//   a</span>
</code></pre>
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          </div>
          <h2 id="eventemitter-once-eventname-listener" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-once-eventname-listener" aria-hidden="true">#</a> EventEmitter.once(eventName,
            listener)#</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any} 事件名</li>
            <li><code><span class="token property">listener</span></code> {Function} 回调函数</li>
          </ul>
          <p>添加一个单次 listener 函数到名为 eventName 的事件。 下次触发 eventName 事件时，监听器会被移除，然后调用。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>server<span class="token punctuation">.</span><span class="token function">once</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token parameter">stream</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;首次调用！&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
              <div class="line-number"></div>
              <div class="line-number"></div>
              <div class="line-number"></div>
            </div>
          </div>
          <p>返回一个 EventEmitter 引用，可以链式调用。</p>
          <p>默认情况下，事件监听器会按照添加的顺序依次调用。 emitter.prependOnceListener() 方法可用于将事件监听器添加到监听器数组的开头。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code><span class="token keyword">const</span> myEE <span class="token operator">=</span> events<span class="token punctuation">.</span><span class="token function">emitter</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">once</span><span class="token punctuation">(</span><span class="token string">&#39;foo&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;a&#39;</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">prependOnceListener</span><span class="token punctuation">(</span><span class="token string">&#39;foo&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;b&#39;</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
myEE<span class="token punctuation">.</span><span class="token function">emit</span><span class="token punctuation">(</span><span class="token string">&#39;foo&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 打印:</span>
<span class="token comment">//   b</span>
<span class="token comment">//   a</span>
</code></pre>
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          </div>
          <h2 id="eventemitter-prependlistener-eventname-listener" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-prependlistener-eventname-listener" aria-hidden="true">#</a>
            EventEmitter.prependListener(eventName, listener)</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any} 事件名</li>
            <li><code><span class="token property">listener</span></code> {Function} 回调函数</li>
          </ul>
          <p>添加 listener 函数到名为 eventName 的事件的监听器数组的开头。 不会检查 listener 是否已被添加。 多次调用并传入相同的 eventName 和 listener 会导致
            listener 被添加与调用多次。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>server<span class="token punctuation">.</span><span class="token function">prependListener</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token parameter">stream</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;有连接！&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
              <div class="line-number"></div>
              <div class="line-number"></div>
              <div class="line-number"></div>
            </div>
          </div>
          <p>返回一个 EventEmitter 引用，可以链式调用。</p>
          <h2 id="eventemitter-prependoncelistener-eventname-listener" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-prependoncelistener-eventname-listener" aria-hidden="true">#</a>
            EventEmitter.prependOnceListener(eventName, listener)</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any} 事件名</li>
            <li><code><span class="token property">listener</span></code> {Function} 回调函数</li>
          </ul>
          <p>添加一个单次 listener 函数到名为 eventName 的事件的监听器数组的开头。 下次触发 eventName 事件时，监听器会被移除，然后调用。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>server<span class="token punctuation">.</span><span class="token function">prependOnceListener</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token parameter">stream</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;首次调用！&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
              <div class="line-number"></div>
              <div class="line-number"></div>
              <div class="line-number"></div>
            </div>
          </div>
          <p>返回一个 EventEmitter 引用，可以链式调用。</p>
          <h2 id="eventemitter-removealllisteners-eventname" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-removealllisteners-eventname" aria-hidden="true">#</a>
            EventEmitter.removeAllListeners([eventName])</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any}</li>
          </ul>
          <p>移除全部或指定 eventName 的监听器。</p>
          <p>注意，在代码中移除其他地方添加的监听器是一个不好的做法，尤其是当 EventEmitter 实例是其他组件或模块创建的。</p>
          <p>返回一个 EventEmitter 引用，可以链式调用。</p>
          <h2 id="eventemitter-removelistener-eventname-listener" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-removelistener-eventname-listener" aria-hidden="true">#</a>
            EventEmitter.removeListener(eventName, listener)</h2>
          <ul>
            <li><code><span class="token property">eventName</span></code> {any}</li>
            <li><code><span class="token property">listener</span></code> {Function}</li>
          </ul>
          <p>从名为 eventName 的事件的监听器数组中移除指定的 listener。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code><span class="token keyword">const</span> <span class="token function-variable function">callback</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token parameter">stream</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;有连接！&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>
server<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">,</span> callback<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// ...</span>
server<span class="token punctuation">.</span><span class="token function">removeListener</span><span class="token punctuation">(</span><span class="token string">&#39;connection&#39;</span><span class="token punctuation">,</span> callback<span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
              <div class="line-number"></div>
              <div class="line-number"></div>
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            </div>
          </div>
          <p>removeListener 最多只会从监听器数组里移除一个监听器实例。 如果任何单一的监听器被多次添加到指定 eventName 的监听器数组中，则必须多次调用 removeListener 才能移除每个实例。
          </p>
          <p>注意，一旦一个事件被触发，所有绑定到它的监听器都会按顺序依次触发。 这意味着，在事件触发后、最后一个监听器完成执行前，任何 removeListener() 或 removeAllListeners()
            调用都不会从 emit() 中移除它们。 随后的事件会像预期的那样发生。</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code><span class="token keyword">const</span> myEmitter <span class="token operator">=</span> events<span class="token punctuation">.</span><span class="token function">emitter</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">const</span> <span class="token function-variable function">callbackA</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;A&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  myEmitter<span class="token punctuation">.</span><span class="token function">removeListener</span><span class="token punctuation">(</span><span class="token string">&#39;event&#39;</span><span class="token punctuation">,</span> callbackB<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>

<span class="token keyword">const</span> <span class="token function-variable function">callbackB</span> <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
  console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">&#39;B&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">;</span>

myEmitter<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;event&#39;</span><span class="token punctuation">,</span> callbackA<span class="token punctuation">)</span><span class="token punctuation">;</span>

myEmitter<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&#39;event&#39;</span><span class="token punctuation">,</span> callbackB<span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment">// callbackA 移除了监听器 callbackB，但它依然会被调用。</span>
<span class="token comment">// 触发是内部的监听器数组为 [callbackA, callbackB]</span>
myEmitter<span class="token punctuation">.</span><span class="token function">emit</span><span class="token punctuation">(</span><span class="token string">&#39;event&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 打印:</span>
<span class="token comment">//   A</span>
<span class="token comment">//   B</span>

<span class="token comment">// callbackB 被移除了。</span>
<span class="token comment">// 内部监听器数组为 [callbackA]</span>
myEmitter<span class="token punctuation">.</span><span class="token function">emit</span><span class="token punctuation">(</span><span class="token string">&#39;event&#39;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">// 打印:</span>
<span class="token comment">//   A</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
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            </div>
          </div>
          <p>因为监听器是使用内部数组进行管理的，所以调用它会改变在监听器被移除后注册的任何监听器的位置索引。 虽然这不会影响监听器的调用顺序，但意味着由 emitter.listeners()
            方法返回的监听器数组副本需要被重新创建。</p>
          <p>返回一个 EventEmitter 引用，可以链式调用。</p>
          <h2 id="eventemitter-setmaxlisteners-n" tabindex="-1"><a class="header-anchor"
              href="#eventemitter-setmaxlisteners-n" aria-hidden="true">#</a> EventEmitter.setMaxListeners(n)</h2>
          <ul>
            <li><code><span class="token property">n</span></code> {number}</li>
          </ul>
          <p>默认情况下，如果为特定事件添加了超过 10 个监听器，则 EventEmitter 会打印一个警告。 此限制有助于寻找内存泄露。 但是，并不是所有的事件都要被限为 10 个。
            emitter.setMaxListeners() 方法允许修改指定的 EventEmitter 实例的限制。 值设为 Infinity（或 0）表明不限制监听器的数量。</p>
          <p>返回一个 EventEmitter 引用，可以链式调用。</p>
          <h1 id="events-broadcast-脚本间广播" tabindex="-1"><a class="header-anchor" href="#events-broadcast-脚本间广播"
              aria-hidden="true">#</a> events.broadcast: 脚本间广播</h1>
          <p>
            脚本间通信除了使用engines模块提供的<code>ScriptEngine<span class="token punctuation">.</span><span class="token function">emit</span><span class="token punctuation">(</span><span class="token punctuation">)</span></code>方法以外，也可以使用events模块提供的broadcast广播。
          </p>
          <p>
            events.broadcast本身是一个EventEmitter，但它的事件是在脚本间共享的，所有脚本都能发送和监听这些事件；事件处理会在脚本主线程执行（后续可能加入函数<code><span class="token function">onThisThread</span><span class="token punctuation">(</span>eventName<span class="token punctuation">,</span> <span class="token operator">...</span>args<span class="token punctuation">)</span></code>来提供在其他线程执行的能力）。
          </p>
          <p>例如在一个脚本发送一个广播hello:</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>events<span class="token punctuation">.</span>broadcast<span class="token punctuation">.</span><span class="token function">emit</span><span class="token punctuation">(</span><span class="token string">&quot;hello&quot;</span><span class="token punctuation">,</span> <span class="token string">&quot;小明&quot;</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
            <div class="line-numbers" aria-hidden="true">
              <div class="line-number"></div>
            </div>
          </div>
          <p>在其他脚本中监听并处理：</p>
          <div class="language-javascript ext-js line-numbers-mode">
            <pre class="language-javascript"><code>events<span class="token punctuation">.</span>broadcast<span class="token punctuation">.</span><span class="token function">on</span><span class="token punctuation">(</span><span class="token string">&quot;hello&quot;</span><span class="token punctuation">,</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">name</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
    <span class="token function">toast</span><span class="token punctuation">(</span><span class="token string">&quot;你好, &quot;</span> <span class="token operator">+</span> name<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">//保持脚本运行</span>
<span class="token function">setInterval</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token operator">=&gt;</span><span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token number">1000</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre>
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              <div class="line-number"></div>
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            </div>
          </div>
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